During the Cold War, why were the USA and USSR enemies?

A question that has spawned many a historians career!
In essence, it was mutual distrust of each other that kept the Cold War going. After WWII, both superpowers wanted to contain Germany however had very different ideas of doing it - the USSR wanted to crush them and the USA wanted to further integrate them into Europe to be unable to rise independently again.
Additionally, they had very different economic ideologies - the individualism of Capitalist USA and the state collectivism of Communist Soviet Russia - however this was a backseat to the struggle for political dominance